Understanding the characteristics of microphysical processes in the rapid intensity changes of tropical cyclones over the Bay of Bengal

Abstract

This study aimed to understand the microphysical processes that affect rapid intensity changes of tropical cyclones (TCs) over the Bay of Bengal (BoB). Four representative TCs were simulated using the Weather Research and Forecasting model with storm tracking nested configuration (at 9‐km and 3‐km resolution). Results indicate that the inner‐core heating strongly correlated (r > 0.85) with the precipitated compared to non‐precipitated hydrometeors. Furthermore, the vertical distribution of hydrometeors and heating is dependent on inner‐core updrafts and relative humidity. A novel composite analysis of microphysical processes indicates that the warmer (2 K) inner core is close to saturation (>90%) with excess water vapor (>2–3 × 10−3 kg·kg−1), which enhances the latent heat release (LHR) through condensation below the freezing level during the rapid intensification (RI) onset. In addition, during RI, strong updrafts transport the water vapor (>2 × 10−3 kg·kg−1) and cloud liquid water (2.5 × 10−4 kg·kg−1) to above freezing level, and enhance the LHR because of deposition and freezing respectively. The increased precipitating particles in the saturated inner core also enhance LHR. The symmetric convection structured by the atmospheric moisture causes the formation of prolonged RI episodes, as seen in TC Phailin. During rapid weakening (RW), asymmetric and relatively fewer hydrometeors are evident, along with the presence of weak updrafts and strong shear. The dry‐air intrusion into the inner core also causes the cooling processes (evaporation and sublimation). The enhancement or reduction of moist static energy and potential vorticity is associated with increased or reduced LHR in the TC rapid intensity changes.

On magnitudes of rapid intensification and destruction of tropical cyclones over the North Indian Ocean

“…Nekkali,Osuri, Das, and Niyogi (2022) mention that consecutive RI episodes (more than one) are observed in some RI TCs. Therefore, a total of 165 RI cases were noticed among a total of 50 RI TCs during 1990–2021.…”

“…Over the NIO region, the maximum energy increased by 9 × 10 6 J·m −2 with an average of 6 × 10 6 J·m −2 in TP2 than in TP1 (Figure 8d). The increases in the most static energy are beneficial to the RI of cyclones (Bhalachandran et al, 2019; Mohanty et al, 2021; Nekkali, Osuri, Das, & Niyogi, 2022).…”

“…The importance of ocean (such as sea surface temperature [SST] and tropical cyclone heat potential) and atmospheric (shear and moisture) conditions in the RI has also been established from the modelling studies (Bhalachandran et al, 2019;Lin et al, 2009;Mohan et al, 2022;Nadimpalli et al, 2023;Osuri et al, 2017). Similarly, Nekkali, Osuri, Das, and Niyogi (2022) have demonstrated the positive role of relative humidity and convective heating in RI onset and maintenance of consecutive RI periods. The inability to resolve multi-scale interactions is one of the reasons for underestimating RI intensity events over the NIO using the weather research and forecasting mesoscale model (Singh et al, 2022).…”

“…On the other hand, the prediction of RI poses challenges to the numerical weather prediction community and disaster management in operational and mitigation efforts (Rappaport et al, 2012; Tallapragada et al, 2016; Tallapragada & Kieu, 2014). RI is a multi‐scale process affected by both environmental and inner‐core processes, which can be modulated by the ocean and atmospheric interactions (Chen & Gopalakrishnan, 2015; Kaplan et al, 2015; Nekkali, Osuri, Das, & Niyogi, 2022; Osuri et al, 2017; Wu & Cheng, 1999).…”